NECY Farm ~ Nutrition, Education, Community & Youth!
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America's Food & Health Crisis
Our Food Supply Madness
Factors Affecting Food's Nutrition
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Factors Affecting Food Nutrition

Pre-Harvest Considerations

While studies vary, there is significant evidence demonstrating that produce has lost substantial nutritional quality in the last 70 years.
The Organic Consumers Association cites several other studies with similar findings: A Kushi Institute analysis of nutrient data from 1975 to 1997 found that average calcium levels in 12 fresh vegetables dropped 27 percent; iron levels 37 percent; vitamin A levels 21 percent, and vitamin C levels 30 percent. A similar study of British nutrient data from 1930 to 1980, published in the British Food Journal, found that in 20 vegetables the average calcium content had declined 19 percent; iron 22 percent; and potassium 14 percent. Yet another study concluded that one would have to eat eight oranges today to derive the same amount of Vitamin A as our grandparents would have gotten from one.28
Soil Quality: The majority of food today comes from large farms, specializing in just a few crops. Repeated annual planting of a single crop depletes topsoil quality. The soil type (sand, clay, loam, etc.), the quality of the soil biome, organic particles, etc. also play a large part. Many plants have preferences.28

Weather Conditions: Is the plant getting its preferred amount of sunlight and water? Plants adjust to their environments but not always for the better.

Climate: Is the crop getting its preferred temperature? Some do well in cooler weather (leafy greens) and some like heat (tomatoes, etc.). When they don't get what they want/need, nutrition can suffer.

Ambient Carbon Dioxide (CO2): A landmark study recently showed that rising CO2 levels have precipitated 95 percent of plant species on earth, including ones we eat like wheat, rice, barley and potatoes, to offer an average of 8% less volume of important minerals like calcium, potassium, zinc and iron.31 As CO2 rises, plants are creating a nearly corresponding amount of additional starch. Just what we need: less nutrition and more carbs, right?

Cultivar or Breed: Heirloom varieties of most plants typically have better nutrition profiles. Popular plant hybrids are usually created to resist drought or heat, improve yields, flavor or appearance, increase resiliency from specific diseases (powdery mildew), shipping or processing etc. While occasional hybrids offer improved nutrition, I haven't heard of any created for that specific purpose.

Post-Harvest Considerations

These are the things, we as consumers can most affect, and truthfully, have the greatest impact.

Freshness: Plants are still alive after harvest. Their struggle to remain viable consumes nutrients.
After picking, fruits and vegetables continue to breathe. This process, called respiration, breaks down stored organic materials, such as carbohydrates, proteins and fats, and leads to loss of food value, flavor and nutrients.29
After harvest plants are also influenced by their own enzymes, causing loss of nutrients and color, as well as flavor changes. Think of week-old corn on the cob.

Ripeness: Many fruits (like tomatoes or bananas) will continue to ripen after harvest. That process consumes nutrients as well.

Storage: How old are the fruit/veggies in your refrigerator? The longer they are held, the less nutritious items can become. As an example, spinach can lose 90% of its vitamin C content within 24 hours of harvest, and 50 percent of its folate and carotenoids within a week. By the time it's purchased in the grocery store, it's often more than a week old.30

Oxidation: Once you breach the skin of a plant you begin to diminish its healthy antioxidants. In our bodies nutrient-derived antioxidant small molecules (vitamin E, vitamin C, carotenes, flavonoids, glutathione, uric acid, and taurine) help to mitigate free radicals.35 When you expose produce 'flesh' to the air, you begin to consume antioxidants. Cutting, dicing, blending, etc. all diminish nutrients to a greater or lesser degree. Don't prep produce in advance.

Cooking: Cooking methods have a substantial impact on nutrition. Most nutrients are either fat or water soluble. Judicious use of fats is not the enemy.36 Some fat dramatically assists the body in breaking down fat soluble nutrients, vitamins A, D, E and K. In general, the more water or heat used in the cooking process, the lower the remaining nutrients. Do you boil vegetables? Do you see leftover 'colored' water? That's where a significant amount of the nutrients have gone.